1. Field
Although not so limited in its utility or scope, implementations of the present invention are particularly well suited for incorporation in intra-facility transport systems such as those used in moving mail pieces through various stages of processing in a mail processing facility, for example.
2. Brief Description of an Illustrative Environment and Related Art
Large-scale material handling operations frequently involve the use of intra-facility transport systems such as conveyor belts and power roller conveyors. A module of a typical power roller conveyor includes a support structure defined by first and second laterally spaced, elongated frame members arranged in parallel and extending along a central longitudinal axis. Extending between, and supported by, the parallel frame members is a plurality of rollers, each of which rollers rotates about an axis perpendicular to the central longitudinal axis and parallel to the axes of other rollers among the plurality. The axes of the rollers are typically spaced apart in accordance with recognized industry-standard specifications. For instance, the roller spacing (i.e., distance between the roller axes) of a typical power roller conveyor in a mail-processing facility is 3 inches. Regardless of the roller spacing peculiar to a particular industry or application, the roller spacing in any particular power roller conveyor is typically fixed.
A typical module of a power roller conveyor includes at least one drive roller and a plurality of xe2x80x9cdrivenxe2x80x9d rollers. In some instances, the drive roller is mechanically linked to a motor through, for example, a belt, chain or drive shaft so that the motor can selectively rotate the drive roller. In other, typically more modern, configurations, the drive roller typically contains the motor internally. Driven rollers are mechanically linked to the drive roller, either directly or through intervening driven rollers, by belts or xe2x80x9co-rings,xe2x80x9d for example. FIG. A illustrates a typical arrangement of driven rollers in relation to a single drive roller from which the driven rollers draw power. It is common for the drive roller to be among the central rollers along a power roller conveyor module because such an arrangement centers the torque transmission to the driven rollers.
Power roller conveyors are used to transport objects (e.g., mail piece trays) from one location to another within a mail-processing facility, for example. Frequently, an overall conveyor system comprises numerous roller conveyor modules linked in series. A single roller conveyor module can be used to join one roller conveyor segment to another roller conveyor segment, a roller conveyor segment to a piece of processing equipment or one piece of processing equipment to a second piece of processing equipment, for example. Typically, roller conveyor modules are fabricated in fixed lengths correlating to some whole-number multiple of the fixed roller spacing plus some constant. Difficulties arise, for example, as equipment is replaced and the spacing between a replacement piece of equipment and another fixed point within the facility is not equal to the distance between the replaced piece of equipment and the fixed point or, worse, does not correspond to a whole-number multiple of the fixed roller spacing plus the original constant. Consider the schematic illustration of such a scenario in conjunction with FIGS. B and C. In the original arrangement of FIG. B, first and second conveyor modules are arranged in series between units A and B. Each conveyor module is ten times the fixed roller spacing (frs) plus a constant xe2x80x9ccxe2x80x9d in length and the distance between units A and B is 20 frs+2 c. In FIG. C, unit Bxe2x80x2 has replaced unit B and is set in place a distance equal to 20 frs+2 c+d from unit A, thereby leaving a gap of length d between the second conveyor module and unit Bxe2x80x2.
Situations such as the one illustrated in FIGS. B and C result in dilemmas presenting choices such as adjusting the position of the replacement equipment and changing the roller spacing between two or more rollers near one or both ends of the roller conveyor module. Moving the piece of equipment is often not practical for any of various reasons. A single piece of mail-processing equipment, for example, can measure well in excess of one hundred feet long and weigh several tons. Moreover, these machines are frequently situated between two sets of conveyor apparatus, rendering movement away from one set of conveyor apparatus toward the other impossible. Adjusting the roller spacing near the end of a roller conveyor module presents difficulties of its own. For instance, the frame members may require cutting to shorten them or the addition of custom-cut lengths to lengthen them, new holes need to be bored in the frame members and the rollers mounted in the new holes. An obstacle other than the actual customization of the conveyor module is that changes in the spacing between rollers require drive belts or o-rings of different, and often, non-standard sizes thereby creating a need for customized o-rings.
Accordingly, there exists a need for a roller conveyor module that is adjustable in length and that is adapted for the selective addition and removal of rollers as indicated by a particular situation.
In various embodiments, an adjustable roller conveyor module includes a roller support structure having first and second ends and first and second laterally spaced, elongated frame members arranged in parallel and extending between the first and second ends along a central longitudinal axis. Extending between, and supported by, the parallel frame members is a plurality of rollers, each of which rollers rotates about an axis perpendicular to the central longitudinal axis and parallel to the axes of other rollers among the plurality. The roller axes of the rollers supported by the support structure lie along a roller plane and, in a typical version, are spaced equally in accordance with a predetermined roller-axis spacing. At least one of the first and second ends of the support structure includes a set of extension apparatus adapted for selective extension to, and retention in, various positions in which the extension apparatus extends beyond the end of the support structure, thereby rendering the overall length of the support structure adjustable. The extension apparatus is adapted for selective coupling to, for example, a unit of equipment (e.g., another conveyor module) adjacent the conveyor module from which it depends. In a typical embodiment, each set of extension apparatus is infinitely positionable, and selectively retainable, between a fully retracted and a fully extended position. That is, the extension apparatus can be selectively retained in any position of an infinite number of positions along a continuum between the fully retracted and extended positions.
In another embodiment, an adjustable roller conveyor module includes first and second support structures. Each of the first and second support structures has first and second laterally spaced, elongated frame members arranged in parallel and extending along a central longitudinal axis. Extending between, and supported by, the parallel frame members is a plurality of rollers, each of which rollers rotates about an axis which, in a typical embodiment, is perpendicular to the central longitudinal axis and parallel to the axes of other rollers among the plurality. A typical embodiment is further characterized in that the roller axes of the rollers supported by each support structure lie along a roller plane and are spaced equally in accordance with a predetermined roller-axis spacing.
In various embodiments, the roller axes of the rollers supported by the first support structure are coplanar with the roller axes of the rollers supported by the second support structure. Accordingly, in a typical embodiment, one of the first and second support structures is reciprocably received between the elongated frame members of the other of the first and second support structures such that one support structure is regarded as an outer support structure and the other support structure is regarded as an inner support structure. Moreover, to accommodate the linear retraction of the inner support structure into (e.g., between the first and second frame members of) the outer support structure, each roller of a selected set of rollers of the outer support structure is selectively removable. With the removal of each successive roller in the outer support structure, the inner support structure is permitted to linearly retract into the outer support structure by a distant corresponding to the fixed spacing between the rollers of the outer support structure. Conversely, as the inner support structure is extended, rollers may be added to the outer support structure to eliminate xe2x80x9cgapsxe2x80x9d in roller-spacing continuity.
In some versions, the elongated frame members of the outer and inner support structures include roller-mounting apertures, each of which apertures is adapted for receiving an end a roller axle. The roller-mounting apertures are equally spaced in accordance with a predetermined roller-axis spacing. The roller-mounting apertures are furthermore situated so that the elongated frame members of the inner support structure are slidable into incremental positions in which roller-mounting apertures of the inner support structure are aligned with roller-mounting apertures of the outer support structure in an overlapping relationship. In a typical version, the axles of rollers mounted in overlapping apertures extend through the opposed roller-mounting apertures of the inner support structure and at least partially into the opposed roller-mounting apertures of the outer support structure. Rollers mounted within the roller-mounting apertures of both the inner and outer support structures are regarded as members of a more broadly definable set of rollers referred to as xe2x80x9csharedxe2x80x9d rollers. It will be appreciated that the number of shared rollers depends in various implementations on the degree of extension of the inner support structure with respect to the outer support structure.
In various aspects, the outer support structure includes extension apparatus capable of extending beyond the xe2x80x9cfree endxe2x80x9d of the outer support structure opposite the end beyond which the inner support structure extends for adjusting the overall length of the conveyor module. Various versions further include extension apparatus for similarly extending beyond the free end of the inner support structure. The capacity for the extension apparatus in any particular version to extend xe2x80x9cbeyond the xe2x80x98free endxe2x80x99xe2x80x9d of the support structure in no way implies that, in such a version, the extension apparatus must be retractable into a position in which it does not extend beyond the free end to some degree. For instance, in a version illustrative of the preceding point, the xe2x80x9cmost retractedxe2x80x9d position of the extension apparatus is one in which the extension apparatus still protrudes beyond the free end; however, even in this version, the extension apparatus is capable of xe2x80x9cextending beyond the free endxe2x80x9d of the support structure, albeit to some greater degree than when it is in its most retracted position. The same non-limiting interpretation applies equally to single-support-structure conveyor modules that include extension apparatus.
When extension members adjacent each end of the overall conveyor module are each in a first retracted position and, for example, the outer and inner support structures are aligned for the inclusion of one or more shared rollers, the overall length of the module is equal to a whole-number multiple of the predetermined roller spacing plus some first constant. In various versions, each extension member is extendable beyond the free end of the support structure from which it depends by a distance equal to at least one-half the predetermined roller-axis spacing so that the overall length of the conveyor module can be extended, without translating the inner support structure with respect to the outer support structure, by a length at least as long as the predetermined roller-axis spacing. It will be appreciated that a conveyor module has some maximally retracted length in which some maximum number of rollers is shared and the extension members are fully retracted and some maximally extended length in which some minimum number of rollers is shared and the extension members are maximally extended. It will furthermore be appreciated that when each extension member is adapted for selective retention in any position between its first retracted position and a second extended position corresponding to an overall increase in the length of the support structure of at least one-half of the predetermined roller-axis spacing beyond the minimum assumable length of the support structure from which in depends, the conveyor module can be adjusted to assume any overall length between its maximally retracted and maximally extended lengths.